Multi-wheel-driving vehicle

ABSTRACT

A multi-wheel-driving vehicle including at least three parallel axles each of which is provided on both ends thereof with respective drive wheels and including power dividing means for permitting the rotary speed among the axles, is improved in its effect of braking so that the braking force of fewer brakes is effectively transmitted to all drive wheels of a vehicle according to a simple braking operation by a driver. The power dividing means, for example, a differential gear unit, includes an input member and a pair of output members, like differential side gears, each of which interlocks with at least one of the axles so as to differentially share a driving force received by the input member between the pair of output members. The multi-wheel-driving vehicle comprises a brake provided on one of the at least three axles, and locking means for locking the input member and the pair of output members together, so that when a driver operates a brake-operating tool for braking, the locking means is automatically operated to lock the input member and the pair of output members together.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable

STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT

Not applicable

REFERENCE TO MICROFICHE APPENDIX/SEQUENCE LISTING/TABLE/COMPUTER PROGRAMLISTING APPENDIX

(Submitted on a Compact Disc and an Incorporation-by-reference of theMaterial on the Compact Disc)

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multi-wheel-driving vehicle providedwith not less than six drive wheels. More particularly, the presentinvention relates to a technique for improving the braking capacity ofthe multi-wheel-driving vehicle, as well as compactness and cost savingsin its construction.

2. Background Art

Conventionally, there is a multi-wheel-driving vehicle having three ormore axles disposed in parallel, each of which is provided at its leftand right ends with respective drive wheels. Generally, each axle isdivided into left and right halves which are differentially connectedwith each other through a differential.

U.S. Pat. No. 4,050,534 discloses a power transmission system for such amulti-wheel-driving vehicle wherein engine power is distributed amongthree axles as follows. The torque output from a transmission is firstlytransmitted to a tandem axle mechanism, i.e., a center differentialwhich differentially connects a pair of coaxial first and secondtransmission shafts. The tandem axle mechanism distributes a part of thetorque to the frontmost (steerable) axle and the rearmost axle throughthe first transmission shaft and the remainder of the torque to themiddle axle (second rear axle) through the second transmission shaft,thereby nicely balancing the torque among the three axles. However, insuch a cited conventional power distribution structure, the frontmostaxle for steerable front drive wheels is drivingly synchronized with therearmost axle for unsteerable rear drive wheels, so that the driving ofthe front wheels is restricted while turning by the driving of the rearwheels, thereby hindering a smooth steering of the vehicle. For avoidingsuch a problem, it is effective to have the axle of the steerable wheelsdrivingly differentially connected with the other axles.

Furthermore, this cited document does not disclose an arrangement ofbrakes. In the cited art, if only the middle axle of the three isprovided thereon with a brake, the tandem axle mechanism prevents thebraking force applied thereon from being effectively transmitted to thefrontmost and rearmost axles. On the other hand, if a brake is justprovided on either the front axle or the rearmost axle, the brakingforce applied on the axle is transmitted to the other of the front orrearmost axle because the two axles interlock with each other throughthe first transmission shaft. However, the braking force is noteffectively transmitted to the middle axle interlocking with the secondtransmission shaft. Thus, to effectively stop the vehicle, the middleaxle and at least one of the frontmost and rearmost axles needrespective brakes, whereby at least two brakes are necessary.

Furthermore, as mentioned above, each axle is generally divided into twohalves differentially connected with each other. If only one of thehalves is provided thereon with a brake, the braking force cannot beeffectively transmitted to the other half. If the first and secondtransmission shafts of the tandem axle mechanism are locked together andif the halves of each axle are locked together, a braking forcegenerated by fewer brakes can be effectively transmitted to all axles,thereby improving compactness of the vehicle and increasingcost-savings. It is preferable that such differential-locking operationsare automatically performed due to the driver's braking operation so asto facilitate the driver's work.

BRIEF SUMMARY OF THE INVENTION

A first object of the present invention is to provide amulti-wheel-driving vehicle including three or more axles arranged inparallel along a longitudinal axis of the vehicle. Each of the axles isprovided on each end thereof with a respective drive wheel. One of thethree or more axles is a steering axle provided with steerable drivewheels, and includes power dividing means for permitting rotary speedamong the axles, wherein the steering axle is drivingly differentiallyconnected with the other axles so that the steerable drive wheels can bedriven while receiving nicely distributed power.

To achieve the first object, the vehicle is provided with a pair oftransmission members like coaxial shafts between which a first powerdividing means, such as a one-way clutch, is interposed. The steeringaxle synchronously interlocks with one of the transmission members, andat least another axle, preferably, all the axles other than the steeringaxle interlock with the other transmission member. Power is transmittedthrough the first power dividing means between both the transmissionmembers while the first power dividing means allows a difference ofrotary speed between the transmission members.

Alternatively, the vehicle is provided with a second power dividingmeans, such as a differential, comprising an input member and a pair ofoutput members (like coaxial shafts) provided thereon with respectivedifferential side gears. Each of the output members synchronouslyinterlocks with at least one axle. The steering axle synchronouslyinterlocks with either the input member or one of the output members ofthe second power dividing means. Preferably, only the steering axle ofthe three or more axles synchronously interlocks with one of the outputmembers. At least one axle other than the steering axle interlocks withthe other output member. The remaining axle or axles interlock witheither the input member or the other output member.

Furthermore, three or more transaxle devices may be arranged in tandemalong the longitudinal axis of the vehicle so that each of the transaxledevices includes input means and each of the three or more axles servesas output means. One of the three or more transaxle devices is a maintransaxle device whose input means receives power from a prime moverprior to the other transaxle devices. Another of the transaxle devicesis a steering transaxle device whose axle is the steering axle.Preferably, the steering transaxle device is separate from the maintransaxle device.

In this case, a continuous variable transmission may be interposedbetween the prime mover and the input means of the main transaxledevice. If the input means is provided on one side of the main transaxledevice, a power-take-out portion of the main transaxle device fortransmitting power to another transaxle device may be provided onanother opposite side of the main transaxle device.

If the power dividing means is the above-mentioned first power dividingmeans interposed between a pair of first and second transmission membersfor transmitting power from the first transmission member to the secondtransmission member, the input means of the main transaxle devicesynchronously interlocks with the first transmission member, and atleast one input means of the other transaxle devices synchronouslyinterlocks with the second transmission member. Preferably, only theaxle of the steering transaxle device synchronously interlocks with thesecond transmission member, and all the axles of the other transaxledevices synchronously interlock with the first transmission member.

If the power dividing means is the second power dividing means includingthe input member and the pair of output members, power taken from themain transaxle device is transmitted into the input member of the secondpower dividing means. Each of all the input member and the outputmembers of the second power dividing means synchronously interlocks withat least one of all the axles of the three or more transaxle devices.Alternatively, all the axles of the three or more transaxle devices maydistributively synchronously interlock with the pair of output membersof the second power dividing means so that at least one axlesynchronously interlocks with each of the output members of the secondpower dividing means. Preferably, only the steering axle synchronouslyinterlocks with one of the output members of the second power dividingmeans.

A second object of the present invention is to provide themulti-wheel-driving vehicle as mentioned above with a braking force,supplied by fewer brakes, that is effectively transmitted to all drivewheels of a vehicle in response to a simple braking operation by adriver, thereby enhancing braking effectiveness and reducing the cost ofproviding brakes.

To achieve the second object, a brake such as a wet-type is provided onone of the three or more axles. In the case that the three or more axlesserve as output means of respective transaxle device including inputmeans, a brake is provided on a transmission system or the axle in themain transaxle device. If the first power dividing means is utilized,locking means is provided for locking the pair of transmission memberstogether, so that when a driver operates a manual brake-operating toolfor braking, the locking means is automatically operated to lock thepair of transmission members together.

If the second power dividing means is utilized, locking means isprovided for locking the input member and the pair of output memberstogether, so that when the driver operates the brake-operating tool forbraking, the locking means is automatically operated to lock the inputmember and the pair of output members together.

Additionally, if the axle provided thereon with the brake is dividedinto two halves differentially connected with each other through adifferential and the brake is provided on one of the halves,differential-locking means is provided for locking the two halvestogether. Thus, when a driver operates the brake-operating tool forbraking, the differential-locking means is automatically operated tolock the halves together.

Other and further objects of the present invention will appear morefully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

FIG. 1 is a schematic diagram of a driving transmission system of amulti-wheel-driving vehicle including front, middle and rear transaxledevices disposed in tandem along a longitudinal axis of the vehicleaccording to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of the rear transaxle device of the samemulti-wheel-driving vehicle;

FIG. 3 is a sectional developed view of the interior of the reartransaxle device;

FIG. 4 is a schematic diagram of the middle transaxle device of the samemulti-wheel-driving vehicle;

FIG. 5 is a sectional plan view of the interior of the middle transaxledevice;

FIG. 6 is a sectional side view of the same;

FIG. 7 is a schematic diagram of the front transaxle device of the samemulti-wheel-driving vehicle;

FIG. 8 is a hydraulic and electric circuit diagram of a control systemfor brakes and clutches in the driving transmission system of the samemulti-wheel-driving vehicle;

FIG. 9 is a schematic diagram of a driving transmission system of amulti-wheel-driving vehicle according to a second embodiment of thepresent invention;

FIG. 10 is a schematic diagram of a driving transmission system of amulti-wheel-driving vehicle according to a third embodiment of thepresent invention;

FIG. 11 is a hydraulic and electric circuit diagram of a control systemfor braking and differential-locking in the driving transmission systemof the multi-wheel-driving vehicle according to the third embodiment;

FIG. 12 is a schematic diagram of a driving transmission system of amulti-wheel-driving vehicle according to a fourth embodiment of thepresent invention;

FIG. 13 is a schematic diagram of a driving transmission system of amulti-wheel-driving vehicle according to a fifth embodiment of thepresent invention;

FIG. 14 is a schematic diagram of a driving transmission system of amulti-wheel-driving vehicle according to a sixth embodiment of thepresent invention, and

FIG. 15 is a schematic diagram of a driving transmission system of amulti-wheel-driving vehicle according to a seventh embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a multi-wheel-driving vehicle 1 comprises a fronttransaxle device 10 which serves as a steering transaxle device disposedat its front portion, a middle transaxle device 16 disposed at itslongitudinally intermediate portion, and a rear transaxle device 4disposed at its rear portion. Rear transaxle device 4 which serves as amain transaxle device includes a pair of left and right rear axles 8serving as main axles which support at their outer ends respective rearwheels 9. Middle transaxle device 16 includes a pair of left and rightmiddle axles 25 serving as second axles which support at their outerends respective middle wheels 26. Front transaxle device 10 includes apair of left and right front axles 11 serving as steering axles whichsupport at their outer ends respective steerable front wheels 12.

The power of an engine 3, which serves as a prime mover mounted on abody of multi-wheel-driving vehicle 1, is transmitted to rear axles 8 ofrear transaxle device 4 so as to drive rear wheels 9 forward andbackward, thereby making vehicle 1 travel forward and backward. Also, afour-wheel-drive mode in which middle wheels 26 are driven in additionto rear wheels 9 or a six-wheel-drive mode in which front wheels 12 arestill additionally driven can be selectively established by a driver'soperation.

A transmission system for transmitting power from engine 3 to rear axles9 comprises a continuous variable transmission (hereinafter, “CVT”) 7disposed outside rear transaxle device 4 and a speed-changing geartransmission 35 disposed in rear transaxle device 4. CVT 7 is interposedbetween an output shaft 6 of engine 3 and an input shaft 5 ofspeed-changing gear transmission 35. Input shaft 5 projects laterallyoutwardly from one of left and right sides of a rear axle housing 31 ofrear transaxle device 4. A follower split pulley 36 is provided on inputshaft 5 outside housing 31 for constituting CVT 7.

In this embodiment, CVT 7 is a belt-type CVT constituted by splitpulleys and a belt wherein the speed reduction ratio is automaticallysteplessly reduced according to the increase of rotary speed of engine3. However, it may be replaced with a hydrostatic stepless transmissionincluding a hydraulic pump and a hydraulic motor, for example, which ismanually or automatically adjusted in its output rotary speed. Anytransmission mechanism may be interposed between output shaft 6 andinput shaft 5 if it agrees with the requirements.

Description will be given on rear transaxle device 4 with reference toFIGS. 2 and 3. Rear axle housing 31 of rear transaxle device 4 is madeof a pair of left and right housing halves joined together. In housing31 are laterally disposed a drive shaft 37, a counter shaft 41 andcoaxial rear axles 8 in parallel to one another. Drive shaft 37 iscoaxially connected to input shaft 5 through a torque sensor 34. Torquesensor 34 detects various type resistances such as rolling resistance,air resistance, acceleration resistance and grade resistance generatedfrom each of wheels 12, 26 and 9 or the like, and outputs detectionsignals into a controller (not shown). The controller adjusts the degreeof opening of a throttle valve of engine 3 correspondingly to thedetection signals, thereby serving as a torque sensing governor.

In housing 31 is interposed a speed-changing gear transmission 33between drive shaft 37 and counter shaft 41. Drive shaft 37 is fixedlyprovided therearound with a high-speed drive gear 38 and a low-speeddrive gear 39, and notched on its periphery so as to integrally form areverse drive gear 40. A high-speed follower gear 42 and a reversefollower gear 44 are relatively rotatably provided around counter shaft41. High-speed follower gear 42 directly engages with high-speed drivegear 38. Reverse follower gear 44 engages with reverse drive gear 40through an idle gear 45. A low-speed follower gear 43 is relativelyrotatably provided around a boss portion of high-speed follower gear 42so as to directly engage with low-speed drive gear 39.

A spline hub 46 is fixedly disposed around counter shaft 41 betweenlow-speed follower gear 43 and reverse follower gear 44. A gear-changingclutch slider 47 is axially slidably but not relatively rotatablydisposed around spline hub 46. Gear-changing clutch slider 47 is axiallyslidden along counter shaft 41 so as to engage with one of gears 42, 43and 44 provided on counter shaft 41, thereby selectively bringingcounter shaft 41 into a high-speed regularly directed rotation, alow-speed regularly directed rotation or a reversely directed rotation.Also, gear-changing clutch slider 47 can be located at its neutralposition where it does not engage with any of gears 42, 43 and 44.

Vehicle 1 is provided with a manually operable speed-changing tool (notshown) such as a lever interlocking with gear-changing clutch slider 47.The speed-changing tool is shiftable among a high-speed forward drivingposition, a low-speed forward driving position, a reverse drivingposition and a neutral position, thereby sliding gear-changing clutchslider 47 correspondingly.

Counter shaft 41 is notched on its periphery so as to form an outputgear 51 adjacent to one of its ends. Output gear 51 constantly engageswith a ring gear 53 of a main-axle-differential 32 which is disposed inrear axle housing 31 for differentially connecting left and rightcoaxial rear axles 8 with each other.

Main-axle differential 32 will be described. A hollow differentialcasing 52 is disposed coaxially with rear axles 8 and rotatablysupported by housing 31. Ring gear 53 serving as an input gear of themain-axle-differential 32 is fixed around differential casing 52 so asto engage with output gear 51. In differential casing 52, a pinion shaft54 is disposed between facing inner ends of rear axles 8 andperpendicularly to rear axles 8, and is supported by differential casing52 so as to be rotatable together with differential casing 52 centeringaxes of rear axles 8. Pinion shaft 54 is rotatably provided thereon witha pair of pinions 55 adjacent to differential casing 52 into which eachof the ends of pinion shaft 54 is engaged. In differential casing 52,differential side gears 56 are fixedly disposed on respective rear axles8 symmetrically with respect to pinion shaft 54 so as to engage withboth pinions 55.

A main-axle-differential locking mechanism 33 for lockingmain-axle-differential 32 together with both rear axles 8 will bedescribed. The portion of differential casing 52 laterally opposite toring gear 53 is formed into a boss. A main-axle-differential lockingslider 57 is axially slidably disposed around the boss portion ofdifferential casing 52. At least one lock pin 58 is fixed at one endthereof to main-axle-differential locking slider 57 and projects at theother end thereof into differential casing 52 in parallel to rear axles8. The differential side gear 56 disposed adjacent tomain-axle-differential locking slider 57 is provided at its surfacedirected toward main-axle-differential locking slider 57 with a recess59 into which lock pin 58 can be engaged. When differential-lockingslider 52 is slidden along the boss portion of differential casing 52toward main-axle-differential 32, lock pin 58 is moved together withmain-axle differential-locking slider 57 and engaged into recess 59 soas to lock main-axle-differential 32 together with both rear axles 8,thereby making both rear axles 8 rotate at the same rotary speed.

Vehicle 1 is provided with a manually operable differential-locking tool(not shown) such as a lever interlocking with main-axle-differentiallocking slider 57. The differential-locking tool is switchable between alocking position and an unlocking position, thereby selectively lockingor unlocking main-axle-differential 32.

A hydraulic brake 22 of a wet multi-frictional-disc type is provided oneach rear axle 8 in housing 31. As shown in FIG. 8 (as discussed below),vehicle 1 is provided with a brake pedal 19 which is depressed so as tosimultaneously apply brake force onto both rear axles 8 through brakes22.

A PTO casing 15 is fixedly mounted on an outer side surface of rear axlehousing 31 in laterally opposite to input shaft 5. In rear axle housing31, counter shaft 41 is extended at its one end outwardly and coaxiallyconnected to an extension shaft 61 through a coupling 60. Extensionshaft 61 projects into PTO casing 15. A first PTO shaft 63 projectsforward from PTO casing 15. In PTO casing 15, a bevel gear 62 fixed onextension shaft 61 engages with a bevel gear 64 fixed on first PTO shaft63.

Description will be given on middle transaxle device 16 with referenceto FIGS. 4 through 6. An input shaft 82 is disposed longitudinally ofvehicle 1, rotatably supported by a middle axle housing 16 a, andprojects backward from housing 16 a so as to be universally joined withfirst PTO shaft 63 through a propeller shaft 17. In middle axle housing16 a, a clutch gear 86 is fixedly provided around input shaft 82. Acounter shaft 83 is rotatably disposed parallel to input shaft 82 inmiddle axle housing 16 a, and fixedly provided thereon adjacent to itsrear end with a counter gear 84 which constantly engages with clutchgear 86. A front end of counter shaft 83 is formed into a bevel gear 85.

Coaxial left and right middle axles 25 are differentially connected witheach other through a second-axle-differential 89 in middle axle housing16 a. Second-axle-differential 89 for middle axles 25, similar tomain-axle-differential 32 for rear axles 8, comprises a differentialcasing 91, a pinion shaft 92, a pair of pinions 93 and a pair ofdifferential side gears 94. Differential casing 91 is disposed coaxiallywith middle axles 25 and rotatably supported by middle axle housing 16a. A bevel gear 90 serving as an input gear of second-axle-differential89 is fixed around differential casing 91 so as to constantly engagewith bevel gear 85. Pinion shaft 92 is disposed between middle axles 25and perpendicularly to middle axles 25 in differential casing 91 andsupported at its opposite ends by differential casing 91. Pinions 93 arerotatably provided around pinion shaft 92 in differential casing 91 soas to be disposed symmetrically with respect to middle axles 25. Indifferential casing 91 are disposed inner ends of middle axles 25 aroundwhich differential side gears 94 are respectively fixed so as to engagewith both pinions 93.

A second PTO shaft 87 is disposed in middle axle housing 16 a coaxiallywith input shaft 82 and projects forward therefrom. In middle axlehousing 16 a, a front end of input shaft 82 is backwardly recessed and arear end of second PTO shaft 87 is inserted into the recessed front endof input shaft 82. A one-way clutch 20 is interposed between input shaft82 and second PTO shaft 87. One-way clutch 20 is engaged so as totransmit driving force therebetween only when input shaft 82 is rotatedfor forward driving of vehicle 1. On the other hand, one-way clutch 20is disengaged so as to allow a difference in rotary speed between inputshaft 82 and second PTO shaft 87, that is, between middle wheels 26 andfront wheels 12. A center clutch slider 88 is axially slidably disposedaround second PTO shaft 87. A center clutch is constructed betweencenter clutch slider 88 and clutch gear 86 so as to be engaged anddisengaged by sliding of center clutch slider 88.

In this embodiment, middle transaxle device 16 includingsecond-axle-differential 89 is constantly drivingly connected with reartransaxle device 4 including main-axle-differential 32. In the case thata front clutch for drivingly connecting front transaxle device 10 tomiddle transaxle device 16 is engaged, when center clutch slider 88 isslidden backward so as to engage the center clutch, that is, to lockinput shaft 82 and second PTO shaft 87 together regardless of one-wayclutch 20, middle transaxle device 16 and front transaxle device 4 canbe drivingly synchronized with each other, thereby enabling front wheels12 to be driven synchronously with middle wheels 26 and rear wheels 9.

With reference to FIG. 7, description will be given on front transaxledevice 10. An input shaft 14 is disposed longitudinally of vehicle 1,rotatably supported by a front axle housing 10 a, and projects backwardso as to be connected to second PTO shaft 87 through a propeller shaft18 and universal joints. In front axle housing 10 a is a front clutchshaft 95 coaxially disposed with input shaft 14. A front clutch slider96 is axially slidably disposed around front clutch shaft 95. A frontclutch is constructed between the rear end of front clutch slider 96 andthe front end of input shaft 14 so as to be engaged and disengaged bysliding of front clutch slider 96. Front clutch shaft 95 is fixedlyprovided at its front end with a bevel gear 97 so as to constantlyengage with a bevel gear 98 serving as an input gear of athird-axle-differential 99 which differentially connects coaxial leftand right front axles 11 with each other.

Third-axle-differential 99 is constructed almost similarly withmain-axle-differential 32 of rear transaxle device 4 andsecond-axle-differential 89 of middle transaxle device 16. The maindifference is that third-axle-differential 99 for front axles 11 isprovided in its differential casing with multiple frictional discs,thereby serving as a multi-disc-type limited slip differential.

Description will now be given on a control system for brakes 22 andclutch sliders 88 and 96 in accordance with FIG. 8, wherein clutchsliders 88 and 96 are operated so as to effectively transmit the brakingforce generated by brakes 22 in rear transaxle device 4 to middle andfront transaxle devices 16 and 10.

Brake pedal 19 is hydraulically connected to the pair of brakes 22 inrear transaxle device 4 through a hydraulic circuit 100 which comprisesa master cylinder 101, an oil tank 102, an oil filter 103, a manualvalve 104 and an oil passage 105. Oil is supplied from oil tank 102 intomaster cylinder 101 through oil filter 103 and valve 104. Oil passage105 is extended from a discharge port of master cylinder 101 andbranches to both brakes 22.

Master cylinder 101 is provided therein with a piston 107 and a spring108 biasing piston 107 to the initial position. A piston rod 106 isfixedly extended from piston 107 opposite of the discharge port ofmaster cylinder 101 so as to be connected to brake pedal 19. Brake pedal19 is depressed so as to push piston 107 toward the discharge port ofmaster cylinder 101 through piston rod 106 as much as the degree ofdepression of brake pedal 19, thereby discharging oil from mastercylinder 101 into both brakes 22 through oil passage 105 and pressingthe multi-discs of each brake 22 against one another so as to brake bothrear axles 8. When brake pedal 19 is depressed beyond a predetermineddegree, valve 104 is closed so as to stop oil supply into mastercylinder 101, thereby preventing oil from back-flowing to oil tank 102and ensuring the action of piston 107 according to depression of brakepedal 19. When brake pedal 19 is released from the depressing forceapplied thereon, piston 107 and brake pedal 19 are returned to theirinitial position by the biasing force of spring 108.

A switching sensor 48 is disposed adjacent to brake pedal 19 so as to beswitched on by depression of brake pedal 19. Switching sensor 48 iselectrically connected to a controller 30 for controlling the engagingand disengaging of the above-mentioned clutches.

A center clutch lever 121 is disposed beside a driver's seat of vehicle1 for operating center clutch slider 88 disposed in middle transaxledevice 16. A switching sensor 49 is disposed so as to be switched onwhen center clutch lever 121 is located at its clutch-on position. Afront clutch lever 122 is also disposed beside the driver's seat foroperating front clutch slider 96 disposed in front transaxle device 10.A switching sensor 50 is disposed so as to be switched on when frontclutch lever 122 is located at its clutch-on position. Both switchingsensors 49 and 50 are electrically connected to controller 30 so as tosend signals about the positions of levers 121 and 122 to controller 30.

A hydraulic circuit 120 for sliding clutch sliders 88 and 96 comprises ahydraulic pump 110 driven by engine 3, an oil tank 111 for supplying oilto hydraulic pump 110, a pair of hydraulic cylinders 112 serving as adouble actuator for sliding center clutch slider 88, a pair of hydrauliccylinders 113 serving as a double actuator for sliding front clutchslider 96, a solenoid valve 114 for hydraulically controlling cylinders112, a solenoid valve 115 for hydraulically controlling cylinders 113,and a relief valve 116 for controlling the hydraulic pressure inhydraulic circuit 120.

Pistons of both cylinders 112 are fixed to each other and coupled withcenter clutch slider 88. Solenoid valve 114 is switched between twopositions, in each position oil discharged from hydraulic pump 110 issupplied into one of cylinders 112 and simultaneously oil is drainedfrom the other cylinder 112, thereby shifting center clutch slider 88between a clutch-on position and a clutch-off position. The same is truefor cylinders 113 and solenoid valve 115 regarding the front clutchcomprising front clutch slider 96.

When brake pedal 19 is not depressed, switching sensor 48 is off,whereby solenoid valves 114 and 115 are controlled by controller 30 soas to locate each of clutch sliders 88 and 96 between its clutch-onposition and its clutch-off position according to the positions ofcenter clutch lever 121 and front clutch lever 122 which are detected byswitching sensors 49 and 50. When brake pedal 19 is depressed, switchingsensor 48 is switched on so that both solenoid valves 114 and 115 arecontrolled by controller 30 so as to forceably locate both clutchsliders 88 and 96 at their clutch-on positions regardless of thepositions of levers 121 and 122.

Due to such a control system, when brakes 22 are operated for braking,the three transaxle devices 4, 16 and 10 are drivingly connectedtogether so as to make the braking force applied onto rear axles 8effectively transmitted to middle axles 25 and front axles 8, wherebyall of the six wheels 9, 26 and 12 are braked, thereby shortening thebraking distance of vehicle 1.

Alternatively, during the depression of brake pedal 19, only solenoidvalve 114 may be forceably controlled for locating center clutch slider88 to its clutch-on position so that rear wheels 9 and middle wheels 26,four wheels in total, are braked.

Description will now be given on various driving transmission systems asmodifications of the above-mentioned first preferred embodiment.Referring to a second embodiment shown in FIG. 9, instead of one-wayclutch 20, a center differential 23 is interposed between input shaft 82and second PTO shaft 87 in middle transaxle device 16 for sharing thetorque transmitted from rear transaxle device 4 between front transaxledevice 10 and middle transaxle device 16, thereby permitting adifference in rotary speed between front wheels 12 and middle wheels 26.Center differential 23 differentially connects both shafts 82 and 87with each other. Input shaft 82 is inserted into a differential casing23 a of center differential 23 so as to make differential casing 23 aintegrally rotatable with input shaft 82. In differential casing 23 aare disposed a pair of differential side gears 23 b and 23 c and a pairof differential pinions 23 d. Differential side gear 23 b is rotatablyprovided around input shaft 82 and is formed integral with clutch gear86 disposed outside differential casing 23 a while differential sidegear 23 c is fixed to second PTO shaft 87. Differential pinions 23 d areinterposed between differential side gears 23 b and 23 c in typicalform.

A center differential locking clutch slider 88′ replacing center clutchslider 88 is axially slidably provided around input shaft 82. A centerdifferential locking clutch is constructed between clutch gear 86 andcenter differential locking clutch slider 88′ so as to be engaged anddisengaged by sliding of center differential locking clutch slider 88′.When center differential locking clutch slider 88′ is located so as toengage the center differential locking clutch, clutch gear 86 and inputshaft 82 are joined together so as to drivingly synchronize middletransaxle device 16 and rear transaxle device 4 with each other, andalso, center differential 23 is locked together with both shafts 82 and87, whereby front transaxle device 10 is synchronously driven withmiddle and rear transaxle devices 16 and 4 if the front clutch isengaged.

When brake pedal 19 is depressed so as to switch on switching sensor 48,center differential locking clutch slider 88′ and front clutch slider 96are forceably located at their clutch-on positions for transmittingbraking force applied on rear axles 8 to middle and front axles 25 and11. Other undescribed parts of this second embodiment are similar withthose of the first embodiment.

Referring to a third embodiment shown in FIG. 10, center differential 23and the center differential locking clutch are disposed in middletransaxle device 16 similar to the second embodiment. In rear transaxledevice 4, only one brake 22 is disposed on one of left and right rearaxles 8.

The third embodiment employs a control system for operation of the frontclutch and differential-locking of main-axle-differential 32 and centerdifferential 23 as shown in FIG. 11, wherein the front clutch areengaged and main-axle-differential 32 and center differential 23 aredifferentially locked so as to effectively transmit the braking forcegenerated by single brake 22 in rear transaxle device 4 to middle andfront transaxle devices 16 and 10.

Beside the driver's seat of vehicle 1 are provided a center differentiallocking lever 121′ replacing center clutch lever 121, and amain-axle-differential locking lever 125. Each of differential lockinglevers 121′ and 125 is shiftable between its locking position and itsunlocking position. A switching sensor 49′ is provided so as to beswitched on when center differential locking lever 121′ is located atits locking position. A switching sensor 65 is provided so as to beswitched on when main-axle-differential locking lever 125 is located atits locking position.

In a hydraulic circuit 120′ for operating sliders 57, 88′ and 96, thepair of hydraulic cylinders 112 are provided for sliding centerdifferential locking clutch slider 88′ between its locking and unlockingpositions, and solenoid valve 114 is provided for controllingoil-supplying and oil-draining of cylinders 112. Additionally, a pair ofhydraulic cylinders 123 serve as a double actuator for slidingmain-axle-differential locking slider 57 between its locking andunlocking positions. A solenoid valve 124, electrically connected tocontroller 30, is provided for controlling oil-supplying andoil-draining of cylinders 123. Other structures and parts are similarwith those of hydraulic circuit 120 shown in FIG. 8.

Further, the controlling parts for main-axle-differential lockingmechanism 33 such as main-axle-differential locking lever 125, hydrauliccylinders 123 and solenoid valve 124 are also provided in the controlsystem of the first embodiment shown in FIG. 8. These features areomitted in FIG. 8 because they are irrelevant to the description of theclutch-controlling for effectively transmitting braking force to allwheels 9, 26 and 12 of vehicle 1.

In the third embodiment, the forced controlling ofmain-axle-differential locking mechanism 33 is required for transmittingthe braking force of only one brake 22 to both rear axles 8. Therefore,in this embodiment, when brake pedal 19 is depressed, solenoid valves114, 115 and 124 are controlled by controller 30 so as to forceablylocate main-axle-differential locking slider 57, center differentiallocking clutch slider 88′ and front clutch slider 96 at their locking orclutch-on positions. Thus, the braking force generated by only one brake22 provided on one rear axle 8 can be effectively transmitted to theother rear axle 8 and also transmitted to both middle wheels 26 and bothfront wheels 12, thereby effectively stopping vehicle 1.

Four preferred embodiments shown in FIGS. 12 to 15, wherein middle axles25 serves as main axles and rear axles 8 serves as second axles, havesuch a common structure as follows. Power of engine 3 is, first,transmitted to middle transaxle device 16 serving as a main transaxledevice, and driving force is transmitted from middle transaxle device 16to rear transaxle device 4 and front transaxle device 10. Speed-changinggear transmission 35, torque sensor 34, main-axle-differential 32 andmain-axle-differential locking mechanism 33 are exchanged withsecond-axle-differential 89 between rear transaxle device 4 and middletransaxle device 16. Main-axle-differential 32 differentially connectscoaxial left and right middle axles 25 with each other. Only one ofmiddle axles 25 is provided thereon with brake 22.Second-axle-differential 89 differentially connects coaxial left andright rear axles 8 with each other. Rear transaxle device 4 is providedwith a forwardly extended input shaft 13 which receives driving forcetransmitted from middle transaxle device 16.

In each of the embodiments shown in FIGS. 12 through 15 (except for thatshown in FIG. 14), middle transaxle device 16 is provided on one outerside of its middle axle housing 16 a, preferably in opposite to itsinput side, with a PTO casing 15′ replacing PTO casing 15. A rear PTOshaft 82′ is extended backward from PTO casing 15′ so as to beuniversally joined to input shaft 13 of rear transaxle device 4 throughpropeller shaft 17. A front PTO shaft 87′ is extended forward from PTOcasing 15′ so as to be universally joined to input shaft 14 of fronttransaxle device 10 through propeller shaft 18.

Referring to a fourth embodiment shown in FIG. 12, counter shaft 41 (orextension shaft 61 coaxially extended from counter shaft 41) projectsinto PTO casing 15′. In PTO casing 15′, a bevel gear 28 fixed to countershaft 41 constantly engages with a bevel gear 27 fixed to rear PTO shaft82′. Rear PTO shaft 82′ and front PTO shaft 87′ are disposed coaxiallywith each other. One-way clutch 20 is interposed between rear PTO shaft82′ and front PTO shaft 87′, thereby permitting a difference of rotaryspeed therebetween. Center clutch slider 88 is axially slidably disposedaround front PTO shaft 87′. A center clutch is constructed betweencenter clutch slider 88 and bevel gear 27 fixed to rear PTO shaft 82′.

In this embodiment, due to such a structure, rear transaxle device 4 isconstantly drivingly connected with middle transaxle device 16. When thecenter clutch is engaged while the front clutch in front transaxlecasing 10 is engaged, front transaxle device 10 is also synchronouslydriven with middle and rear transaxle devices 16 and 4.

The fourth embodiment employs a similar control system as shown in FIG.8 so that, when brake pedal 19 is depressed, both the center clutchincluding center clutch slider 88 and the front clutch including frontclutch slider 96 are forceably engaged for effectively transmittingbraking force from one middle axle 25 serving as a main axle to rearaxles 8 serving as second axles and front axles 11 serving as steeringaxles. However, for effectively braking all wheels of vehicle 1, inaddition to that shown in FIG. 8, main-axle-differential locking slider57 is required to be forceably slidden so as to lockmain-axle-differential 32 as shown in FIG. 11.

Referring to a fifth embodiment shown in FIG. 13, in middle axle housing16 a of middle transaxle device 16, a second counter shaft 71 and athird counter shaft 72 are disposed parallel to counter shaft 41 andmiddle axles 25. Third counter shaft 72 is extended into PTO casing 15′so as to engage with rear PTO shaft 82′ through bevel gears. Adifferential output shaft 73 is disposed coaxially with second countershaft 71 and extended into PTO casing 15′ so as to engage with front PTOshaft 87′ through bevel gears.

In middle axle housing 16 a, center differential 23′ is interposedbetween second counter shaft 71 and differential output shaft 73 so asto differentially connecting both shafts 71 and 73 with each other.Output gear 51, fixedly provided on counter shaft 41, constantly engageswith a ring gear 74 of center differential 23′ so that the torque ofcounter shaft 41 is transmitted to center differential 23′ and sharedbetween second counter shaft 71 and differential output shaft 73.

Center differential locking clutch slider 88′ is axially slidablydisposed around second counter shaft 71 so as to engage with anddisengage from a differential casing 23′a of center differential 23′.When center differential locking clutch slider 88′ is slidden to engagewith differential casing 23′a, center differential 23′ is locked so asto lock second counter shaft 71 and differential output shaft 73together.

A middle-axle-drive gear 75 fixed on second counter shaft 71 constantlyengages with ring gear 53 of main-axle-differential 32 differentiallyconnecting middle axles 25 with each other. A first rear-axle-drive gear76 fixed on second counter shaft 71 constantly engages with a secondrear-axle-drive gear 77 fixed on third counter shaft 72, thereby drivingsecond-axle-differential 89 differentially connecting rear axles 8 witheach other. As a result, a part of the torque of counter shaft 41 sharedby center differential 23′ is transmitted to middle axles 25 and rearaxles 8, and the remainder is transmitted to front axles 11 (while thefront clutch is engaged).

The fifth embodiment employs a similar control system as shown in FIG.11 so that, when brake pedal 19 is depressed, the front clutch includingfront clutch slider 96 is engaged and both center differential 23′ andmain-axle-differential 32 are locked for effectively applying brakingforce to all wheels 9, 26 and 12 of vehicle 1. In this embodiment, themain axle provided thereon with brake 22 is not necessarily driven priorto center differenitial 23′ for braking all wheels 9, 26 and 12 becauseall axle-differentials 32, 89 and 99 are synchronously driven andconnected together by the locking of center differential 23′ duringbraking.

Referring to a sixth embodiment shown in FIG. 14, a pair of PTO casings15″ are fixedly provided on middle axle housing 16 a, preferably onopposite outer sides thereof. One PTO casing 15″ supports rear PTO shaft82′ extending backward, and the other supports front PTO shaft 87′extending forward. Instead of shafts 71, 72 and 73, middle transaxledevice 16 of this embodiment is provided with coaxial first and seconddifferential output shafts 78 and 79. Center differential 23′ isinterposed between shafts 78 and 79, and ring gear 74 of centerdifferential 23′ constantly engages with gear 51 fixed on counter shaft41.

First differential output shaft 78 is extended into one of PTO casings15″ so as to engage with front PTO shaft 87′ though bevel gears. Seconddifferential output shaft 79 is extended into the other of PTO casings15″ so as to engage with rear PTO shaft 82′ through bevel gears. A gear80 is fixed on second differential output shaft 79 so as to constantlyengage with ring gear 53 of main-axle-differential 32 differentiallyconnecting middle axles 25 with each other.

Therefore, similarly with the fifth embodiment, center differential 23′distributively transmits a part of the torque of counter shaft 41 tofront axles 11 through first differential output shaft 78 and theremainder to middle and rear axles 25 and 8 through second differentialoutput shaft 79.

The sixth embodiment also employs the similar control system shown inFIG. 11 so that, when brake pedal 19 is depressed, the front clutchincluding front clutch slider 96 is engaged and both center differential23′ and main-axle-differential 32 are locked for effectively applyingbraking force to all wheels 9, 26 and 12 of vehicle 1.

Referring to a seventh embodiment shown in FIG. 15, middle transaxledevice 16 is provided at its one outer side with one PTO casing 15′ inwhich rear PTO shaft 82′ and front PTO shaft 87′ are disposed coaxiallywith each other. In PTO casing 15′, center differential 23 is interposedbetween rear PTO shaft 82′ and front PTO shaft 87′ so as todifferentially connecting both shafts 82′ and 87′ with each other.

In middle axle housing 16 a, a second counter shaft 65 is disposedparallel to counter shaft 41. Output gear 51 is fixed on second countershaft 65 so as to constantly engage with ring gear 53 ofmain-axle-differential 32. Counter shaft 41 and second counter shaft 65are extended into PTO casing 15′. In PTO casing 15′, a bevel gear 68fixed on counter shaft 41 constantly engages with a bevel ring gear 69fixed to differential casing 23 a of center differential 23. Centerdifferential locking clutch slider 88′ is axially slidably disposedaround front PTO shaft 87′ so as to engage with and disengage fromdifferential casing 23 a. Thus, center differential 23 distributivelytransmits a part of the torque of counter shaft 41 to front axles 11through front PTO shaft 87′ and the remainder to middle and rear axles25 and 8 through rear PTO shaft 82′.

The seventh embodiment also employs the similar control system shown inFIG. 11 so that, when brake pedal 19 is depressed, the front clutchincluding front clutch slider 96 is engaged and both center differential23 and main-axle-differential 32 are locked for effectively applyingbraking force to all wheels 9, 26 and 12 of vehicle 1.

Alternatively, in each of the fourth to seventh embodiments, both middleaxles 25 may be provided thereon with respective brakes 22. In thiscase, similarly with the first and second embodiments, the forcedlocking of main-axle-differential 32 for effectively transmittingbraking force to both middle axles 25 is unnecessary when brake pedal 15is depressed.

In each of the first to seventh embodiments, brake 22 may bealternatively provided on a member such as counter shaft 41 prior tomain-axle-differential 32 or center differential 23 or 23′. In thiscase, main-axle-differential 32, when braking, is not necessarilylocked, however, it is preferably locked for effectively applying thebraking force onto both the main axles.

For further or other embodiments of the present invention than the abovementioned embodiments shown in the drawings, main differential 23 may bedisposed in front transaxle device 10 so as to receive power from engine3 prior to middle and rear transaxle devices 16 and 4. In this case,input means of middle and rear transaxle devices 16 and 4 maysynchronously interlock with the primary side of one-way clutch 20, andfront (steering) axle 11 may synchronously interlock with the secondaryside of one-way clutch 20. Alternatively, input means of middle and reartransaxle devices 16 and 4 may synchronously interlock with one ofdifferential side gears 23 d of center differential 23, and front(steering) axle 11 may synchronously interlock with the otherdifferential side gear 23 d.

Although the invention has been described in its preferred form with acertain degree of particularity, it is understood that the presentdisclosure of the preferred form has been changed in the details ofconstruction and the combination and arrangement of parts may beresorted to without departing from the spirit and the scope of theinvention as hereinafter claimed.

1. A multi-wheel-driving vehicle, comprising: three or more axlesarranged in parallel along a longitudinal axis of said vehicle, each ofsaid axles provided on both ends thereof with respective drive wheels,wherein one of said three or more axles is a steering axle provided withsteerable drive wheels; first and second transmission members, whereinsaid steering axle synchronously interlocks with said secondtransmission member, and wherein all the other axles synchronouslyinterlock with said first transmission member; and power dividing meansinterposed between said first and second transmission members, whereinpower is transmitted directly to said first transmission member andthrough said power dividing means to said second transmission memberwhile said power dividing means permits a difference of rotary speedbetween said first and second transmission members.
 2. Themulti-wheel-driving vehicle as set forth in claim 1, wherein said firstand second transmission members are a pair of shafts disposed coaxiallywith each other, and wherein said power dividing means is a one-wayclutch interposed between said pair of shafts.
 3. Themulti-wheel-driving vehicle as set forth in claim 1, wherein said powertransmitted through said power dividing means is directed from saidfirst transmission member to said second transmission member.
 4. Themulti-wheel-driving vehicle as set forth in claim 1, wherein saidsteering axle is a frontmost axle of said three or more axles.
 5. Themulti-wheel-driving vehicle as set forth in claim 1, wherein only saidsteering axle of all said three or more axles synchronously interlockswith said second transmission member.
 6. The multi-wheel-driving vehicleas set forth in claim 5, wherein said axles are three in total, andwherein the two axles other than said steering axle synchronouslyinterlock with said first transmission member.
 7. Themulti-wheel-driving vehicle as set forth in claim 1, further comprising:a brake provided on one of said three or more axles; a manualbrake-operating tool for operating said brake; and locking means forlocking said first and second transmission members together, wherein,when said brake-operating tool is operated for braking, said lockingmeans is automatically operated to lock said first and secondtransmission members together.
 8. The multi-wheel-driving vehicle as setforth in claim 7, wherein said brake is a wet type brake.
 9. Themulti-wheel-driving vehicle as set forth in claim 7, wherein said oneaxle provided thereon with said brake is not said steering axle.
 10. Themulti-wheel-driving vehicle as set forth in claim 7, wherein said axleprovided thereon with said brake is divided into two halves, and whereinsaid brake is provided on one of said halves, further comprising: adifferential differentially connecting said halves with each other; anddifferential-locking means for locking said two halves together, whereinwhen said brake-operating tool is operated for braking, saiddifferential-locking means is automatically operated to lock said halvestogether.
 11. A multi-wheel-driving vehicle, comprising: three or moreaxles arranged in parallel along a longitudinal axis of said vehicle,each of said axles provided on both ends thereof with respective drivewheels, wherein one of said three or more axles is a steering axleprovided with steerable drive wheels; and power dividing means whereinsaid power dividing means is a differential gear unit including an inputshaft, an output gear and an output shaft, wherein said power dividingmeans differentially shares power transmitted into said input shaftbetween said output gear and said output shaft, wherein each of saidinput shaft, said output gear and said output shaft synchronouslyinterlocks with at least one of said three or more axles.
 12. Themulti-wheel-driving vehicle as set forth in claim 11, wherein saidsteering axle is the most front one of said three or more axles.
 13. Themulti-wheel-driving vehicle as set forth in claim 11, wherein saidsteering axle synchronously interlocks with only one of said inputshaft, said output gear and said output shaft.
 14. Themulti-wheel-driving vehicle as set forth in claim 13, wherein said axlesare three in total, and wherein the two axles other than said steeringaxle respectively synchronously interlock with said input shaft, saidoutput gear and said output shaft.
 15. The multi-wheel-driving vehicleas set forth in claim 13, wherein said steering axle synchronouslyinterlocks with one of said output gear and said output shaft.
 16. Themulti-wheel-driving vehicle as set forth in claim 15, wherein only saidsteering axle of all said three or more axles synchronously interlockswith said output shaft.
 17. The multi-wheel-driving vehicle as set forthin claim 16, wherein said axles are three in total, and wherein the twoaxles other than said steering axle respectively synchronously interlockwith said input shaft and the output gear.
 18. The multi-wheel-drivingvehicle as set forth in claim 11, further comprising: a brake providedon one of said at least three axles; a manual brake-operating tool foroperating said brake; and locking means for locking said output gear andsaid output shaft together, wherein, when said brake-operating tool isoperated for braking, said locking means is automatically operated tolock said output gear and said output shaft together.
 19. Themulti-wheel-driving vehicle as set forth in claim 18, wherein said brakeis a wet type brake.
 20. The multi-wheel-driving vehicle as set forth inclaim 18, wherein said one axle provided thereon with said brake is notsaid steering axle.
 21. The multi-wheel-driving vehicle as set forth inclaim 18, wherein said axle provided thereon with said brake is dividedinto two halves, and wherein said brake is provided on one of saidhalves, further comprising: a differential differentially connectingsaid halves with each other; and differential-locking means for lockingsaid two halves together, wherein when said brake-operating tool isoperated for braking, said differential-locking means is automaticallyoperated to lock said halves together.
 22. A multi-wheel-drivingvehicle, comprising: three or more axles arranged in parallel along alongitudinal axis of said vehicle, each of said axles provided on bothends thereof with respective drive wheels, wherein one of said three ormore axles is a steering axle provided with steerable drive wheels; andpower dividing means wherein said power dividing means is a differentialgear unit including an input gear and a pair of output shafts providedthereon with respective differential side gears, wherein said powerdividing means differentially shares power transmitted into said inputgear between said pair of output shafts, wherein each of said three ormore axles synchronously interlocks with one of said output shafts orsaid input gear.
 23. The multi-wheel-driving vehicle as set forth inclaim 22, wherein said steering axle is the most front one of said threeor more axles.
 24. The multi-wheel-driving vehicle as set forth in claim22, wherein said steering axle synchronously interlocks with one of saidoutput shafts.
 25. The multi-wheel-driving vehicle as set forth in claim24, wherein said axles are three in total, and wherein the two axlesother than said steering axle synchronously interlock with the otheroutput shaft.
 26. The multi-wheel-driving vehicle as set forth in claim22, further comprising: a brake provided on one of said at least threeaxles; a manual brake-operating tool for operating said brake; andlocking means for locking said first and second output shafts together,wherein, when said brake-operating tool is operated for braking, saidlocking means is automatically operated to lock said first and secondoutput shafts together.
 27. The multi-wheel-driving vehicle as set forthin claim 26, wherein said brake is a wet type brake.
 28. Themulti-wheel-driving vehicle as set forth in claim 26, wherein said oneaxle provided thereon with said brake is not said steering axle.
 29. Themulti-wheel-driving vehicle as set forth in claim 26, wherein said axleprovided thereon with said brake is divided into two halves, and whereinsaid brake is provided on one of said halves, further comprising: adifferential differentially connecting said halves with each other; anddifferential-locking means for locking said two halves together, whereinwhen said brake-operating tool is operated for braking, saiddifferential-locking means is automatically operated to lock said halvestogether.
 30. A multi-wheel-driving vehicle, comprising: a prime mover;three or more transaxle devices disposed in tandem along a longitudinalaxis of said vehicle, wherein each of said transaxle devices includesinput means and an axle serving as output means, said axle beingprovided on both ends thereof with respective drive wheels, wherein oneof said three or more transaxle devices is a main transaxle device whoseinput means receives power from said prime mover prior to the othertransaxle devices, and wherein one of said three or more transaxledevices is a steering transaxle device whose axle is provided withsteerable drive wheels; first and second transmission members, whereinpower of said prime mover is taken out from said main transaxle deviceto said first transmission member, and wherein said second transmissionmember synchronously interlocks with both said first transmission memberand said input means of at least one of the other transaxle devicesother than said main transaxle device; and power dividing meansinterposed between said pair of transmission members, wherein said poweris transmitted directly to said first transmission member and throughsaid power dividing means from said first transmission member to saidsecond transmission member while said power dividing means permits adifference of rotary speed between said first and second transmissionmembers.
 31. The multi-wheel-driving vehicle as set forth in claim 30,wherein said first and second transmission members are a pair of shaftsdisposed coaxially with each other, and wherein said power dividingmeans is a one-way clutch interposed between said pair of shafts. 32.The multi-wheel-driving vehicle as set forth in claim 30, wherein saidsteering transaxle device is a frontmost transaxle device of said threeor more transaxle devices.
 33. The multi-wheel-driving vehicle as setforth in claim 30, wherein only said axle of said steering transaxledevice of all said axles of said three or more transaxle devicessynchronously interlocks with one of said first and second transmissionmembers.
 34. The multi-wheel-driving vehicle as set forth in claim 30,wherein said steering transaxle device is other than said main transaxledevice so that an input means of said steering transaxle devicesynchronously interlocks with said second transmission member.
 35. Themulti-wheel-driving vehicle as set forth in claim 34, wherein only saidaxle of said steering transaxle device of all said axles of said threeor more transaxle devices synchronously interlocks with said secondtransmission member.
 36. The multi-wheel-driving vehicle as set forth inclaim 35, wherein said transaxle device are three in total, and whereinsaid axles of the other two transaxle devices than said steeringtransaxle device synchronously interlock with said first transmissionmember.
 37. The multi-wheel-driving vehicle as set forth in claim 30,further comprising: a continuously variable transmission interposedbetween said prime mover and said input means of said main transaxledevice.
 38. The multi-wheel-driving vehicle as set forth in claim 37,further comprising: a power-taking out portion for transmitting power tosaid first transmission member provided on an opposite side of said maintransaxle device to said input means of said main transaxle device. 39.The multi-wheel-driving vehicle as set forth in claim 30, furthercomprising: a brake provided on a transmission system or said axle insaid main transaxle device; a manual brake-operating tool for operatingsaid brake; and locking means for locking said input member and saidpair of output members of said power dividing means together, wherein,when said brake-operating tool is operated for braking, said lockingmeans is automatically operated to lock said input means and said outputmeans together.
 40. The multi-wheel-driving vehicle as set forth inclaim 39, wherein said brake is a wet type brake.
 41. Themulti-wheel-driving vehicle as set forth in claim 39, wherein said maintransaxle device is not said steering transaxle device.
 42. Themulti-wheel-driving vehicle as set forth in claim 39, wherein said axleprovided thereon with said brake is divided into two halves, and whereinsaid brake is provided on one of said halves, further comprising: adifferential differentially connecting said halves with each other; anddifferential-locking means for locking said two halves together, whereinwhen said brake-operating tool is operated for braking, saiddifferential-locking means is automatically operated to lock said halvestogether.
 43. A multi-wheel-driving vehicle, comprising: a prime mover;three or more transaxle devices disposed in tandem along a longitudinalaxis of said vehicle, wherein each of said transaxle devices includes aninput shaft or input gear and an axle serving as output means, said axlebeing provided on both ends thereof with respective drive wheels,wherein one of said three or more transaxle devices is a main transaxledevice whose input shaft or input gear receives power from said primemover prior to the other transaxle devices, and wherein one of saidthree or more transaxle devices is a steering transaxle device whoseaxle is provided with steerable drive wheels; and power dividing means,wherein said power dividing means is a differential gear unit includingan input gear and a pair of output shafts provided thereon withrespective differential side gears, wherein said power dividing meansdifferentially shares power transmitted into said input gear betweensaid pair of output shafts, wherein said input gear and said pair ofoutput shafts synchronously interlock with at least one of said axle ofsaid main transaxle device and said input means of the other transaxledevices other than said main transaxle device.
 44. Themulti-wheel-driving vehicle as set forth in claim 43, wherein said pairof output shafts are coaxial.
 45. The multi-wheel-driving vehicle as setforth in claim 43, wherein said steering transaxle device is a frontmosttransaxle device of said three or more transaxle devices.
 46. Themulti-wheel-driving vehicle as set forth in claim 43, wherein only saidaxle of said steering transaxle device synchronously interlocks withonly one of all said input gear and said output shafts of said powerdividing means.
 47. The multi-wheel-driving vehicle as set forth inclaim 43, wherein said steering transaxle device is not said maintransaxle device so that said input shaft of said steering transaxledevice synchronously interlocks with one of said output shafts of saidpower dividing means.
 48. The multi-wheel-driving vehicle as set forthin claim 47, wherein only said axle of said steering transaxle devicesynchronously interlocks with said one output shaft of said powerdividing means.
 49. The multi-wheel-driving vehicle as set forth inclaim 48, wherein said transaxle device are three in total, wherein saidaxle of said main transaxle device synchronously interlocks with saidinput gear of said power dividing means, and wherein said input shaft orinput gear of the other one transaxle device than both said maintransaxle device and said steering transaxle device synchronouslyinterlocks with the other output shaft of said power dividing means. 50.The multi-wheel-driving vehicle as set forth in claim 43, furthercomprising: a continuously variable transmission interposed between saidprime mover and said input shaft or input gear of said main transaxledevice.
 51. The multi-wheel-driving vehicle as set forth in claim 50,further comprising: a power-taking out portion for transmitting power tosaid input gear provided on an opposite side of said main transaxledevice to said input shaft or input gear of said transaxle device. 52.The multi-wheel-driving vehicle as set forth in claim 43, furthercomprising: a brake provided on a transmission system or said axle insaid main transaxle device; a manual brake-operating tool for operatingsaid brake; and locking means for locking said input gear and said pairof output shafts of said power dividing means together, wherein, whensaid brake-operating tool is operated for braking, said locking means isautomatically operated to lock said input gear and said pair of outputshafts together.
 53. The multi-wheel-driving vehicle as set forth inclaim 52, wherein said brake is a wet type brake.
 54. Themulti-wheel-driving vehicle as set forth in claim 52, wherein said maintransaxle device is not said steering transaxle device.
 55. Themulti-wheel-driving vehicle as set forth in claim 52, wherein said axleprovided thereon with said brake is divided into two halves, and whereinsaid brake is provided on one of said halves, further comprising: adifferential differentially connecting said halves with each other; anddifferential-locking means for locking said two halves together, whereinwhen said brake-operating tool is operated for braking, saiddifferential-locking means is automatically operated to lock said halvestogether.
 56. The multi-wheel-driving vehicle as set forth in claim 1,comprising: a first drive train, wherein said first drive train isdisposed at one lateral side of the vehicle so as to drivingly connectan output shaft of the prime mover to a transmission.
 57. Themulti-wheel-driving vehicle as set forth in claim 56, comprising: asecond drive train, wherein said second drive train is disposedlaterally opposite said first drive train so as to drivingly connectsaid three or more axles.